Improved control of anthracnose rot in loquat fruit by a combination treatment of Pichia membranifaciens with CaCl(2).

The beneficial effect of 2% CaCl(2) (w/v) on the antagonistic yeast Pichia membranifaciens for control of anthracnose rot caused by Colletotrichum acutatum in postharvest loquat fruit (Eriobotrya japonica L.) and the possible mechanisms involved were investigated. The results showed that treatment with P. membranifaciens at 1x10(8) CFU ml(-1) or 2% CaCl(2) alone both resulted in significantly smaller lesion diameter and lower disease incidence of anthracnose rot on loquat fruit wounds compared with the controls. The biocontrol activity of P. membranifaciens on the disease was enhanced by the addition of 2% CaCl(2), the combined treatment of P. membranifaciens with CaCl(2) resulted in a remarkably improved control of the disease in comparison with the treatment of P. membranifaciens or CaCl(2) alone. P. membranifaciens in combination with CaCl(2) induced higher activities of two defense-related enzymes chitinase and beta-1,3-glucanase in loquat fruit than applying the yeast or CaCl(2) alone. The in vitro experiment showed that the addition of 2% CaCl(2) in the suspensions of P. membranifaciens significantly inhibited spore germination and germ tube elongation of C. acutatum than the yeast or CaCl(2) alone. However, adding CaCl(2) did not significantly influence the population of P. membranifaciens in NYDB medium or fruit wounds. These results suggest that CaCl(2) could improve the biocontrol activity of P. membranifaciens on anthracnose rot in loquat fruit. It is postulated that the improved control of the disease is directly because of the higher inhibitory effect on pathogen growth and indirectly because of the enhanced disease resistance in loquat fruit by the combination treatment.